Typewriting machine



Filed April 13 1928 ll II:-

Patented Apr. 29, 1930 UNITED STATES PATENT OFFICE WILLIAM F. HELMOND,0F HARTFORD, oonnncrrcu'r, .assrenon TO- UNDERW'OOD:

ELLIOTT FISHER COMPANY, OF NEW YORK, N. Y., A CORPORATION'OI" DELAWARE'ryrnwnrrme MACHINE Application filed April 13,

This invention relates to revoluble platens for typewriting machines ofthe sound-deadening class.

One of the objects of the invention is to provide an all metal core forthe platen that is durable, cheap, and noise absor ing, without undueweight.

To accomplish the above objects a hollow aluminum tube with aluminumheads is preferably employed, as it is light and not sonorous. J

- In the preferred form of construction, the outer surface of said tubeor core is covered with the usual rubber sheath.

To' absorb or reduce noise, a thin paper flap is coiled into a pluralityof layers, and inserted into the metal core and closely underlies theinner surface thereof. For this purpose, one or more sheets of paper maybe employed, and of such width as to extend very nearly from end to endof the core. Before insertion, the paper receives on one side a thincoat of shellac, .or other moisture-proof material which will insure ahard, smooth, and unstretchable surface, to minimize the tendency of thecoil to set or collapse. Such coat must be thoroughly dry before thepaper is used, to avoid the adhesion of one ply to another or of theouter ply to the inner surface of the core. Were adhesion permitted, thenoisedeadening qualities of inter-lying dead air spaces would be lost.

When the platen is struck by a'type, the resultant noise is in largepart transmitted to the aforementioned rubber sheath. This absorbs partof the vibrations, but, due to its semi-hardness, a large portion istransmitted to the metal core. By the use of aluminum, the sounding-boxeffect is somewhat reduced. This sound-absorbing quality dampens the fewvibrations that start-lengthwise of the core. The major number ofvibrations is transmitted through the walls of the core, and reaches theaforementioned paper coil or flap. The latter through its fibrous orcellular structure absorbs and deadens these vibrations, as theydecreasingly are transmitted through successive plies. This sounddeadening is also helped by the dead air in and between the plies, andin the body of the core.

1928. Serial No. 269,628.

With the above described construction, many advantages are gained. 7

' In the use of paper as a sound deadener, it has been found that aplurality of closely coiled and separate plies is more efiecti've thanis a single or laminated sheet having an equal total thickness. Theetficaey of the plies as a sound-absorbing medium increases in directratio with the number of plies employed. As

inafter appear. I

In the accompanying drawings,

Figure 1 shows a part longitudinal section through the platen.

Figure 2 is an enlarged transverse section through the platen, showing aone piece coil. of paper. 7 r

Figure 3 is an enlarged side view of a sheet of paper, showing amoisture-proof coating applied to one side.

Figure 4 is a transverse section through the platen, showing amultiplicity of paper-sheets formed into a coil. V

Figure 5 is a partial transverse section through the platen, showing asound-deadeningcoil made of ground cork shellacked to thin cardboard.

Referring to the drawings, 10 is an outer Other features and advantageswill here- I jacket or sheath of rubber composition, af-

fordinga sheet-backing surface for the types 11. Said. jacket 10 is atube-tightly superimposed or molded upon a metal tube or core 12, whichmay be interiorly threaded at each end, as at 13, for the reception ofcaps or platen-heads l4. Said caps are hollowed out at 15, andexteriorlythreaded as at 16, to register with the interior threads of the core.

- the hubs 18 may have a plurality of flat faces,

havin for the application of a wrench, in assembling the heads to eachend of the core.

In Figure 2 is shown a one-piece coil or scroll of paper, nested withincore 12, with a thin shellac, varnish or other moisture-proof coating21, which has been previously applied to one side of said paper 22 nextto the core.

Betweenthe several plies of said coil, and between the latter and thesurface of said core, there will remain in places a thin dead air space23, for the purpose hereinbefore explained, and showing one method ofutilizing paper as a sound-deadener.

In Figure 4 is shown a second method, wherein a multiplicity ofpaper-sheets 24,

a coated surface, have been overlappe as at 25, and rolled into a coilwhich has then been inserted in the core and allowed to expand. Thiscoil also retains thin dead air spaces, and in greater amount than inthe first-mentioned one-piece coil. This increased number of dead airspaces is due to the several overlaps, which thus give an addedeffectiveness as a sound-absorbing medium. This building up of a coilfrom separate sheets has other advantages. The fibers in differentsheets may slopeat different angles, and thus zigzag break up, and thebetter absorb, any sound vibrations passing through the wall of thebuilt-up coil. Furthermore, the separate sheets can each be of adifferent structure, or varying structures can be alternated.

Figure v5 shows a third method of building up a sound-deadening coil,for use inside ap a ten-core. 'In the drawing, 26 represents a thinsheet of cardboard, to which has been applied a shellac or other mostureproof coat 2 on which while still wet has been sprinkled a layer ofground cork 28. The whole is allowed to become thoroughly dry, before itis coiled and inserted into the core. In forming the coil, the cardboardmay be so rolled as to become the exterior surface, which when insertedwill easily slide 'to the limit of its expansion against the wall of thecore. Such outward ex ansion is due to the resiliency of the cork, w ichstrives to return to normal after having been compressed by the rollingof the cardboard into a coil. It is obvious,

that instead of cardboard a heavy paper could be used, and that insteadof cork other resilient material might be employed.

With one platen head removed, the dry coated paper is formed into acoil, which may include one long or several short overlapped sheets ofpaper, sufiicient to insure an assembled roll of a plurality of plies.

When this built-up roll is inserted into the platen, its natural wirycharacteristics cause it to expand and tightly hug the inside surface ofthe core, and each ply closely hugs the adjacent outer ply. Such a closehu ing of one surfaceto another is furthere ythe smooth hard surface ofthe coating, which permits each ply to readily slide to the limit of itsoutward expansion. Said expansion is a result of the resiliency of thefibrous or cellular structure of the paper, which tends to restoreitself to a flat state after having been compressed by the coilingoperation. This restoration toa flat state is aided by the coating,which prev'ents expansion or compression on the surface to which thecoating has been applied, so that cells adjacent thereto are notchanged, and retain their initial resiliency. The paper therefore doesnot lose all of its life or springi-ness, and retains its outwardexpanding or uncoiling quality.

From the above descnp tion it will be understodd that thevibration-absorbing coils of paper are not a part of the metal core, butmaintain a lastin contact with the inner face of the tube w1th justenough tension. to insure a firm contact. Variations may be resorted towithin the scope of the invention, and portions of the improvements maybe used without others.

Having thus described my invention, 1

claim:

1. In a typewriter-platen, a core of rubbercoated metal tubing, andmeans to deaden sound vibrations transmitted within the metal tube, saidmeans including a singlecoated varnished paper-sheeting to be looselyrolled up to forma plurality of layers and to be inserted into the tubeso as to hug the inner surface thereof due to the tendency of the coatedside of the paper to expand with sufficient tension to insure a firmcontact against the tube.

2. In a typewriter-platen, a core of rubbercoated metal tubing, andmeans to deaden sound vibrations transmitted within the metal tube, saidmeans including a singlecoated varnished paper-sheeting to be looselyrolledup to form a plurality of layers and to be inserted into the tubein such a way that the outer coated face of the roll tends to expand andhug the inner surface of the spiral air spaces to break up the soundvibrations.

3. In a typewriter-platen. a core of metal tubing, and means to deadensound vibrations of said metal tubing, said means includingpaper-sheeting to be loosely rolled up to form a plurality of layers forinsertion into the tube, one side of the paper being finished with astiff elastic coating to increase the tendency of the paper to unroll soas to closely hug the inner surface of the tube. 1

4. In a typewriter-platen. a core of metal tubing, and means to deadensound vibratitons of said metal tubing, said means includingpaper-sheeting to be loosely rolled up to form a plurality of layers andto be inserted into the tube, one side of the paper being of thecharacter of shellac to increase the tendency of the paper to unroll soas to closely hug the inner surface of the tube.

5. In a typewriter-platen, the combination of a core of metal tubing,and a sound-deadening sheet of paper loosely rolled up to form aplurality of layers and inserted into the tube, the outer side of thepaper having a coating of shellac, tending to cause the paper to unrollso as to closely hug the inner surface of the core.

6. In a typewriter-platen, a core of metal tubing covered with a hardrubber shell, which forms the backing face for the types, and means todeaden sound Vibrations of said metal tubing, said means including asheet of paper to be loosely rolled up to form a plurality of layers andto be inserted into the tube so as to hug the inner surface thereof dueto the tendency of the paper to unroll, this tendency being increased bya stiff elastic coating applied to one side of the paper.

7. A typewriter-platen including the con bination of a tubular metalcore covered with suitable softer material to furnish the working facefor the types, detachable ends for said tubular core to serve asmountings for a platen-shaft, and a sheet of paper, for sounddeadeningpurposes, to be loosely rolled up to form a plurality of layers and tobe inserted into the tube so as to hug the inner surface thereof due tothe tendency of the paper to unroll, this tendency being increased by astiff elastic coating applied to one side of the paper.

8. A typewriter-platen including the combination of a rubber-coatedtubular metal core, platen-heads secured to the ends of the core toprovide asound-enclosing'chamber, and a plurality of rolled-upoverlapping sheets of single-coated varnished paper inserted within thechamber of the tube to uncoil and establish a lasting contact with thetube.

v 9'. A typewriter-platen including the com bination of a tubular metalcore covered with 65 suitable softer material to furnish the workcore.

WILLIAM F. HELMOND.

